Ability to customize auxclasspath based on sourceSet

[vladimirfx]

Currently there is no easy way to use different classpath from source set.

Field sourceSet is private in SpotBugsTask. Please add getter for sourceSet to get this working:

withType<SpotBugsTask> {
        classpath = sourceSet.compileClasspath
    }

[vladimirfx]

Workaround:

    withType<SpotBugsTask> {
        val sourceSetName = name.substring(8).toLowerCase()
        sourceSets.findByName(sourceSetName)?.let {
            classpath = it.compileClasspath
        }
    }